Degenerative disc disease often results in a loss of disc height, which in turn can cause facet and nerve impingement. One standard of care is to remove the disc and fuse the two vertebrae together. However, this can lead to problems at adjacent vertebra levels as those levels become hypermobile to compensate for the loss of mobility at the fused level. A number of devices have therefore been developed to restore height without fusion. Such known devices include artificial discs, pedicle screws with flexible rods, and spacers which may be implanted between spinous processes, referred to herein as interspinous process spacers. Known interspinous process spacers are inserted between the posterior spinous process and can be made of rigid or flexible material. Typically, known interspinous process spacers are placed in the spine in slight distraction to off load the weight of the disc. Interspinous process spacers also typically serve as a stop for extension, and some have attached straps that limit flexion. Many known interspinous spacers are in the shape of an H, wherein the sides of the H prevent the spacer from sliding out from between the processes. Known spacers also are usually made of a metal or a polymer. Ideally, however, bone would be a more suitable material for a spacer, but typical H-shaped bone spacers may result undesirably in the vertebrae fusing to the spacer.